First direct comparison of platelet reactivity and thrombolytic status between Japanese and Western volunteers: Possible relationship to the "Japanese paradox"

OBJECTIVE: To determine and compare thrombotic and endogenous thrombolytic status in Japanese and Western populations.

BACKGROUND: Incidence of coronary heart disease (CHD) and AMI in Japan remains lower than in Western countries. Primary genetic effects are unlikely, given the increased CHD in Japanese migrants. For men, cholesterol and blood pressure have been similar in Japan and the U.S. Dietary factors are implicated, but how these effect CHD is unclear. We postulated that differences in thrombotic and/or thrombolytic status may contribute.

METHODS: We measured thrombotic and thrombolytic status in 100 healthy Japanese (J) from Japan and 100 healthy Westerners (W) from the U.K. using the Global Thrombosis Test (GTT). The GTT employs non-anticoagulated blood to create platelet-rich thrombi under high shear (occlusion time OT; seconds), and then measures the restart of blood flow, due to spontaneous thrombolysis (lysis time LT; seconds).

RESULTS: OT was longer in (J) compared to (W) (545 vs. 364, p3000s) in 18%, compared to none of the Westerners (p<0.0001).

CONCLUSIONS: There are marked differences in thrombotic and thrombolytic status, with (J) having less prothrombotic (longer OT) but less favourable endogenous thrombolytic profile (longer LT). This may be important in the aetiology of thrombotic events. Since platelets and thrombolysis were both inhibited in (J) and yet incidence of AMI is lower, OT would seem more important than LT as a determinant of overall thrombotic risk in this population.